so no, it's not 100% random but I think it is ridiculous that BYU places weight on essays (is it four per applicant now?). If BYU were an elite, small university where the vast majority of applicants have 3.9+ GPAs and 1400+ SAT scores, then it would make sense to hire people to review essays to distinguish applicants.
I think it is a waste of resources to have BYU review 50K-60K essays each year and use those to ding highly qualified applicants. If an applicant has an ecclesiastical endorsement, is a seminary graduate and is in the top quarter of all applicants in terms of combined GPA/ACT, then he/she should be an autoadmit.